When used in cross-DSO mode, CFI will generate calls to special functions rather than trap instructions. For example, instead of generating
if (!InlinedFastCheck(f))
abort();
call *f
CFI generates
if (!InlinedFastCheck(f))
__cfi_slowpath(CallSiteTypeId, f);
call *f
This patch teaches cfi-verify to recognize calls to __cfi_slowpath and abort and treat them as trap functions.
In addition to normal symbols, we also parse the dynamic relocations to handle cross-DSO calls in libraries.
We also extend cfi-verify to recognize other patterns that occur using cross-DSO. For example, some indirect calls are not guarded by a branch to a trap but instead follow a call to __cfi_slowpath. For example:
if (!InlinedFastCheck(f))
call *f
else {
__cfi_slowpath(CallSiteTypeId, f);
call *f
}
In this case, the second call to f is not marked as protected by the current code. We thus recognize if indirect calls directly follow a call to a function that will trap on CFI violations and treat them as protected.
We also ignore indirect calls in the PLT, since on AArch64 each entry contains an indirect call that should not be protected by CFI, and these are labeled incorrectly when debug information is not present.
Differential Revision: https://reviews.llvm.org/D49383
llvm-svn: 340612
Summary:
This patch adds another failure mode for `validateCFIProtection(..)`, wherein any register that affects the indirect control flow instruction is clobbered to between the CFI-check and the instruction's execution.
Also includes a modification to make MCInstrDesc::hasDefOfPhysReg public.
Reviewers: vlad.tsyrklevich
Reviewed By: vlad.tsyrklevich
Subscribers: llvm-commits, pcc, kcc
Differential Revision: https://reviews.llvm.org/D39820
llvm-svn: 318238
Allows users to view GraphResult objects in a DOT directed-graph format. This feature can be turned on through the --print-graphs flag.
Also enabled pretty-printing of instructions in output. Together these features make analysis of unprotected CF instructions much easier by providing a visual control flow graph.
Reviewers: pcc
Subscribers: llvm-commits, kcc, vlad.tsyrklevich
Differential Revision: https://reviews.llvm.org/D39819
llvm-svn: 318211
Summary: Help differentiate code and data by parsing DWARF information. This will reduce false positive rates where data is placed in executable sections and is mistakenly parsed as code, resulting in an inflation in the number of indirect CF instructions (and hence an inflation of the number of unprotected).
Also prints the DWARF line data around the region of each indirect CF instruction.
Reviewers: pcc
Subscribers: probinson, llvm-commits, vlad.tsyrklevich, mgorny, aprantl, kcc
Differential Revision: https://reviews.llvm.org/D38654
llvm-svn: 317050
Implement a localised graph builder for indirect control flow
instructions. Main interface is through GraphBuilder::buildFlowGraph,
which will build a flow graph around an indirect CF instruction. Various
modifications to FileVerifier are also made to const-expose some members
needed for machine code analysis done by the graph builder.
Reviewers: vlad.tsyrklevich
Reviewed By: vlad.tsyrklevich
Subscribers: llvm-commits, kcc, pcc
Differential Revision: https://reviews.llvm.org/D38427
llvm-svn: 316372
Joel Galenson